It is well known to combine sulfonates with carboxylic acid derivates to obtain synergistic behavior in inhibiting corrosion. It is also well known to use emulsions of such corrosion inhibiting compositions and to dilute them with water to provide protective coatings. However, it is not known how to make and use compositions of such ingredients in clear, totally water soluble compositions, i.e., free of emulsions and/or microdispersions, and to provide protective films from them which are strippable in conventional metal working cleaner solutions, while at the same time providing long term protection and the ability to withstand routine handling.
The above-mentioned emulsified compositions provide coatings with protective properties, but, as is a matter of common knowledge and experience, they must be quite thick, e.g., 1-5 mils thick, after drying, to produce reasonable protection. A totally soluble, true solution of such sulfonate compositions would represent a major advance because application and evaporation should leave a very thin film, e.g., 0.05 mils or less, and yet provide excellent protection because the film would be continuous and lack moisture-sensitive emulsifier residues.
It has now been discovered that amine sulfonates and carboxylic acid half esters, optionally including an alkanolamine, can be mixed with water in all proportions to give clear, true solutions. The solutions are true solutions and not emulsions, suspensions or inverted emulsions because they do not exhibit a Tyndall effect.
The compositions can be applied by spraying, dipping, and the like, to protect metal parts with a clear, uniform coating which dries rapidly to leave a nearly invisible non-tacky surface which provides extended protection against corrosion in high humidity conditions. At the same time the coatings are easily removed by stripping, e.g., with conventional alkaline cleaners, leaving chemically clean metallic surfaces.